US Secretary of State John Kerry, left, is greeted by Chinese President Xi Jinping on Saturday. Photo: AP

The world is facing a “critical time”, top US diplomat John Kerry told China’s President Xi Jinping on Saturday, citing tensions on the Korean peninsula, Iran’s nuclear programme and the conflict in Syria.

“Mr President, this is obviously a critical time with some very challenging issues,” Kerry told Xi in the Great Hall of the People in Beijing.

“Issues on the Korean peninsula, the challenge of Iran and nuclear weapons, Syria and the Middle East, and economies around the world that are in need of a boost.”

Kerry arrived from South Korea earlier to press Beijing to help defuse soaring nuclear tensions on the Korean peninsula ahead of an expected missile launch by the North, which conducted a nuclear test in February and a rocket test last December.

Beijing is Pyongyang’s sole major ally and its key provider of aid and trade, and is seen as having unique leverage over the government of Kim Jong-Un, which has issued repeated threats of nuclear war.

But Xi did not refer to the Korean peninsula or other issues raised by Kerry in his opening remarks at the meeting, instead saying that the US-China relationship was “at a new historical stage and has got off to a good start”.

China and the US are both members of the P5+1 nations - the five veto-wielding permanent UN Security Council members and Germany - pressing Iran to give up its what they see as its ambitions to develop nuclear weapons.

The world powers suspect Tehran of developing a covert programme aimed at having the capacity to produce a nuclear bomb. Iran denies this and says its work is being conducted for energy and medical purposes.

China, however, is a key trade partner for the Middle Eastern country and has spoken out against US and European Union sanctions targeting its oil exports.

Washington and Beijing have also been at odds over the conflict in Syria.

China, along with Russia, has vetoed UN Security Council resolutions to introduce sanctions against Bashar al-Assad’s regime in Syria as a two-year conflict has ravaged the country.

As the world’s two biggest economies the US and China are major trade partners, while China is the single biggest buyer of US Treasuries.

But the relationship is also characterised by trade disputes and other tensions, most recently regarding allegations of computer hacking.

A report in February from US security firm Mandiant said a unit of China’s People’s Liberation Army had stolen hundreds of terabytes of data from at least 141 companies, government agencies and other organisations, mostly based in the US.

Beijing has steadfastly denied the allegations and says it is itself a regular victim of cyberattacks.